Improve multiPV mode

Skip all moves during the Non-PV (zero-window) search which will be
searched as PV moves later anyways. We also wake sure the moves will
be reported to the GUI despite they're not being searched — some GUIs
may get confused otherwise, and it would unnecessarily complicate the
code.

Tested with MultiPV=4
STC
http://tests.stockfishchess.org/tests/view/5ce7137c0ebc5925cf070d69
LLR: 2.95 (-2.94,2.94) [0.50,4.50]
Total: 8233 W: 3708 L: 3424 D: 1101

LTC
http://tests.stockfishchess.org/tests/view/5ce798d60ebc5925cf071d17
LLR: 2.95 (-2.94,2.94) [0.00,3.50]
Total: 7369 W: 3197 L: 2911 D: 1261

Closes https://github.com/official-stockfish/Stockfish/pull/2163

No functional change. (in single PV mode)

diff --git a/src/search.cpp b/src/search.cpp
index f682da3ae6e8e9d6c92d709225871c168a3f9464..37fc2ec48a8bfa99b7e4a125f68f540fe1ebaba0 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -292,7 +292,7 @@ void Thread::search() {
   bestValue = delta = alpha = -VALUE_INFINITE;
   beta = VALUE_INFINITE;
 
-  size_t multiPV = Options["MultiPV"];
+  multiPV = Options["MultiPV"];
   Skill skill(Options["Skill Level"]);
 
   // When playing with strength handicap enable MultiPV search that we will
@@ -870,6 +870,12 @@ moves_loop: // When in check, search starts from here
           sync_cout << "info depth " << depth / ONE_PLY
                     << " currmove " << UCI::move(move, pos.is_chess960())
                     << " currmovenumber " << moveCount + thisThread->pvIdx << sync_endl;
+
+      // In MultiPV mode also skip moves which will be searched later as PV moves
+      if (rootNode && std::count(thisThread->rootMoves.begin() + thisThread->pvIdx + 1,
+                                 thisThread->rootMoves.begin() + thisThread->multiPV, move))
+          continue;
+
       if (PvNode)
           (ss+1)->pv = nullptr;
 

diff --git a/src/thread.h b/src/thread.h
index c11d17873df5621ed4892ddbce016332ef55e24c..46ddb49529357f4cbefffa61ff1ecdc2b83bbdb9 100644 (file)
--- a/src/thread.h
+++ b/src/thread.h
@@ -59,7 +59,7 @@ public:
 
   Pawns::Table pawnsTable;
   Material::Table materialTable;
-  size_t pvIdx, pvLast, shuffleExts;
+  size_t pvIdx, multiPV, pvLast, shuffleExts;
   int selDepth, nmpMinPly;
   Color nmpColor;
   std::atomic<uint64_t> nodes, tbHits, bestMoveChanges;